West Nile virus and other mosquito-borne diseases surveillance in Canada: Annual edition 2021 (infographic)

What's the risk?

West Nile virus (WNV) is the leading cause of domestically acquired mosquito-borne diseases (MBD) reported in Canada.

Who's at greater risk?

Advanced age and people with underlying medical conditions (e.g. diabetes, cancer, heart disease) are at increased risk of WNV neurological syndrome.

How to manage?

There is no specific treatment or vaccine for WNV. Patients are treated for their symptoms.

West Nile virus reported in 2021

• 31 positive dead wild birds
• 240 positive mosquito pools
• 19 positive horses
• 43 human cases acquired within Canada
  • 37 clinical cases
    • 62% cases with neurological syndrome
    • 19% cases with non-neurological syndrome
    • 19% cases not specified
    • 2 deaths
  • 6 asymptomatic cases
• 3 travel-related human cases acquired outside of Canada or travel location not specified

When compared to the average of the previous 5 years, a lower number of human cases was observed in 2021. Recurring fluctuations in the number of WNV human infections from year to year are expected.

Other mosquito-borne diseases

• 18 human California serogroup virus infections were reported:
  • 2 identified by the National Microbiology Laboratory
  • 16 reported by Quebec
• 7 cases of Eastern equine encephalitis in horses were reported

Public health recommendations

Avoid becoming infected with WNV and other mosquito-borne diseases by:

• Protecting yourself
  • cover exposed skin
  • use insect repellent with DEET or icaridin
• Reducing surrounding risk
  • eliminate standing water
  • maintain window and door screening